Interpretive Summary: Neospora caninum is a recently recognized protozoan (single celled) parasite of livestock and companion animals. It causes abortion in livestock and paralysis and death in companion animals. Its life cycle and sources of infection are unknown. Diagnosis of abortion due to N. caninum is a problem because currently available tests are insensitive. Scientists at the Beltsville Agricultural Research Center and the University of California, Davis have developed a PCR test to detect DNA from Neospora infected tissues. The PCR should be an additional test for the diagnosis of neosporosis abortion in cattle.

Technical Abstract:
Neospora is a newly recognized genus of pathogenic coccidia, closely related to Toxoplasma gondii, that can cause abortion or congenital disease in a variety of domestic animal hosts. Based on the small subunit ribosomal RNA gene sequence of Neospora and other apicomplexa coccidia, oligonucleotide primers COC-1 and COC-2 were used for PCR amplification of conserved sequences of approximately 300 base pairs in size. A Neospora-specific chemiluminescent probe hybridized to Southern blots of amplification products from Neospora DNA, but not with amplified DNA from the other coccidian parasites tested. A Toxoplasma-specific probe with a single base pair difference between Neospora and Toxoplasma was used to distinguish these parasites by specific Southern blot hybridization. The PCR system detected as few as one Neospora tachyzoite in culture medium or 5 tachyzoites in samples of whole blood or amniotic fluid spiked with Neospora parasites. In addition, Neospora PCR products were successfully amplified from whole blood and amniotic fluid samples of experimentally infected bovine and rhesus macaque fetuses. These results indicate that this PCR and probe hybridization system could be a valuable adjunct to serology and immunohistochemistry for diagnosis of Neospora infections in bovine or primate fetuses.